Miss Sincere and Mr. Good Guy

About this title

First San Dee saw Jing Jai wearing a very expensive dress but the dress is actually mistaken, it got switch with a actress, and San Dee saw Jing Jai looking a an expensive necklace. San Dee thinks Jing Jai is rich and Jing Jai thinks San Dee is rich. A rich family is also trying to find their only child and San Dee is helping them. Who is the child?